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<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="../7-unique.js"></script>
</head>
<body>
  <script>
    //声明一个数组
    const  arr = [1,2,3,2,1,4,5];

    //去重
    console.log(unique3(arr));
  </script>
</body>
</html>